-LRB- Tribune Media Services -RRB- -- When Eileen Mather lands in Mexico City on her way to Tapachula , Mexico , she learns her airline ticket is n't valid . Her airline forces her to buy a new one . Mather asks her online agency , Cheapoair.com , for a refund , but more than six months later , she 's still out $ 879 . Is she also out of options ?

Q : I need your help getting my money back for a plane ticket I had to pay for twice .

Here 's my story : I bought tickets online through Cheapoair.com from Philadelphia to Tapachula , Mexico . When we arrived in Mexico City , Aviacsa Airlines representatives told us that Cheapoair had n't paid for the last leg of our trip . So I had to buy new tickets . Two members of our group also had to pay again .

After I returned home , I faxed all of my documents to a supervisor at Cheapoair . That was six months ago . I 've called her repeatedly and left messages , but no one has contacted me , and I 'm out $ 879 . Is there anything you can do ?

-- Eileen Mather , Glenside , Pennsylvania

A : You should n't have to pay twice for your airline tickets . But you also should n't be too quick to blame Cheapoair for the mix-up .

A lot can go wrong when you 're dealing with a flight schedule that involves multiple carriers . Reservations can be lost , paper tickets and boarding passes can be misread . And , of course , there 's the language issue . When you 're traveling internationally , something can easily get lost in the translation .

Cheapoair may -- or may not -- have been responsible for your non-working tickets . But as your online travel agent , it was responsible for helping you fix it . That 's why you buy from an intermediary and pay a booking fee : so there 's someone to turn to when something goes wrong .

The online agency should n't have kept you in a holding pattern for more than six months . Cheapoair 's `` Golden Guarantee '' promises `` to provide all our customers with 24/7 toll-free number support because we understand the importance of critical last-minute client/traveler needs and requirements for changes to trips . '' I guess offering a toll-free number around the clock does n't necessarily mean your questions will be answered quickly , but you ca n't blame me if I 'm left with that impression .

You could have avoided a lengthy dance with Cheapoair by taking this up with Aviacsa either when you were flying to Tapachula or returning home . If you had arrived at the airport a half-hour earlier , you might have been able to speak with a supervisor and straightened this out . Once you were home , and were running into a brick wall with Cheapoair 's supervisor , I would have tried knocking on the front door again .

Normally , starting a new query through an online form means your complaint will get reviewed again and may be assigned a new case number . A phone call does n't work the same way . After you hang up , your case is basically closed .

I contacted Cheapoair on your behalf . It apologized for the delay and said it contacted Aviasca , but could n't determine why your ticket was n't accepted . An airline representative told Cheapoair it would have to speak to the agent who was working at the ticket counter when you checked in , which was impossible .

Cheapoair refunded the $ 879 you spent on your second ticket .

Christopher Elliott is the ombudsman for National Geographic Traveler magazine . E-mail him at celliott@ngs.org .

Copyright 2009 CHRISTOPHER ELLIOTT , DISTRIBUTED BY TRIBUNE MEDIA SERVICES , INC. .

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Customer booked an international flight through Cheapoair.com

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Ticket for one leg of her flight was not accepted , and she had to buy a new one

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The online agency did not know why her ticket was rejected

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Troubleshooter contacted Cheapoair , and it refunded the customer 's money